Massachusetts Wastewater Practice Exam

To assess the efficiency of screens in an activated carbon system, what sample should be analyzed?

1. Total coliform

2. COD

3. BOD

4. Carbon fines

The correct answer is: Carbon fines

Analyzing carbon fines is essential for assessing the efficiency of screens in an activated carbon system because these fines can indicate how effectively the system is retaining and utilizing the activated carbon. Activated carbon is designed to adsorb contaminants, and if carbon fines are present in the effluent or bypass flow, this suggests that the screens are either not functioning properly or that they are allowing too much carbon to escape. High levels of carbon fines can indicate issues such as channeling, where flow paths develop through the carbon bed, or an overload of contaminants leading to breakdown and disintegration of the carbon itself. In contrast, total coliform, COD (Chemical Oxygen Demand), and BOD (Biochemical Oxygen Demand) do not directly reflect the performance of the screens in retaining activated carbon. Total coliform analyses are more focused on evaluating microbial contamination, while COD and BOD measure the organic load and biodegradable matter in water, which may not provide specific insights into the performance of the activated carbon system in terms of its physical integrity and the retention of carbon particles. Therefore, monitoring carbon fines provides the most relevant information about the screens' efficiency in this context.